I. Introduction
Wireless communication had a rapid pace of revolution over the past few years. From the birth of 1G to the present 5G, a huge transition is observed in people's lifestyle, work, technology etc. The significant increase in the amount of users, throughput and coverage are the primary objectives of wireless standards. “Spectrum” is the crucial resource required to achieve the aforementioned goals. An ever-increasing demand to access the radio spectrum is setting the stage for reviewing the existing radio spectrummanagement practices. Static spectrum assignment policy has limited the use of spectrum resulting in the inefficient usage of this vital resource. The survey report of Federal Communication Commission (FCC) [1] states that, spectrum utilization varies anywhere between 15% to 85 % and 90 % of the time licensed part of the spectrum is unoccupied (fig 1).
Spectrum utilization [1]